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#!/usr/bin/env python3

# Copyright 2014 Brett Slatkin, Pearson Education Inc.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

# Preamble to mimick book environment

import logging

from pprint import pprint

from sys import stdout as STDOUT

# Example 1

def sort_priority(values, group):

def helper(x):

if x in group:

return (0, x)

return (1, x)

values.sort(key=helper)

# Example 2

numbers = [8, 3, 1, 2, 5, 4, 7, 6]

group = {2, 3, 5, 7}

sort_priority(numbers, group)

print(numbers)

# Example 3

def sort_priority2(numbers, group):

found = False

def helper(x):

if x in group:

found = True # Seems simple

return (0, x)

return (1, x)

numbers.sort(key=helper)

return found

# Example 4

found = sort_priority2(numbers, group)

print('Found:', found)

print(numbers)

# Example 5

def sort_priority2(numbers, group):

found = False # Scope: 'sort_priority2'

def helper(x):

if x in group:

found = True # Scope: 'helper' -- Bad!

return (0, x)

return (1, x)

numbers.sort(key=helper)

return found

# Example 6

def sort_priority3(numbers, group):

found = False

def helper(x):

nonlocal found

if x in group:

found = True

return (0, x)

return (1, x)

numbers.sort(key=helper)

return found

# Example 7

found = sort_priority3(numbers, group)

print('Found:', found)

print(numbers)

# Example 8

class Sorter(object):

def __init__(self, group):

self.group = group

self.found = False

def __call__(self, x):

if x in self.group:

self.found = True

return (0, x)

return (1, x)

sorter = Sorter(group)

numbers.sort(key=sorter)

assert sorter.found is True

print('Found:', found)

print(numbers)